Photovoltaic system with managed output and method of managing variability of output from a photovoltaic system

ABSTRACT

Photovoltaic systems with managed output and methods for managing variability of output from photovoltaic systems are described. A system includes a plurality of photovoltaic modules configured to receive and convert solar energy. The system also includes a sensor configured to determine an orientation for each of the plurality of photovoltaic modules, the orientations based on a maximum output from the photovoltaic system. The system also includes an orientation system configured to alter the orientation of one or more of the plurality of photovoltaic modules to provide a reduced output from the photovoltaic system, the reduced output less than the maximum output.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/721,372, filed Mar. 10, 2010, the entire contents of which are herebyincorporated by reference herein.

TECHNICAL FIELD

Embodiments of the present invention are in the field of renewableenergy and, in particular, photovoltaic systems with managed output andmethods of managing variability of output from photovoltaic systems.

BACKGROUND

Common types of photovoltaic deployment include off-grid and on-gridsystems. Off-grid systems are typically small (e.g., 10 s of kilowattsat most) and tied closely to an energy storage system such as a systemof deep-cycle lead acid batteries or, in some cases, to a fueledgen-set. In an off-grid configuration, the energy stored in the batteryacts as a buffer between energy production and demand. As such,short-term variability, such as peak collection, in the solar resourcemay not be an issue. On-grid systems, by contrast, may be quite large,with systems up to the 100 s of megawatts. To date, sizing of on-gridsystems may be such that existing methods of handling load variability(e.g., by provision of ancillary services from generators on the grid)have been sufficient to ensure stability of the grid.

However, with advances in photovoltaic system technology, ever largersystems are being proposed and actually installed for use. Such largersystems may pose challenges for power management in at least two endmarkets, e.g., in island- or micro-grid systems or in very largephotovoltaic plants integrated onto large grids. In either case, theremay be restrictions on the maximum solar energy collection capabilitywith respect to the sizing capability of an associated power conditionerof a power plant. Typically, the proposed method of managing peak orvariable output of renewable generating resources is to add an energystorage component or to subdue plant power production. However, theremay be a lack of reliable, commercially proven, and cost effectivestorage unit compatible with a facility scale at the 100 s of kilowattslevel or higher, or there may be issues associated with invertercontrols or power conditioning controls at an inverter.

Furthermore, one of the major challenges for solar photovoltaic powerplants may be that, at present, owners and operators have very littlecontrol of the electrical output of a power plant in the short-term(e.g., on the hours and minutes scale). Having more control over theoutput of the power plant may be desirable since such control may beused to ensure that plant operations are increasingly economic orpractical. More control may also become a minimum requirement for somelarge photovoltaic power plants, due to limitations of the existingelectrical grid and its ability to cope with load variability. Thecurrent lack of output control in the hourly or minutely timeframe maybe due to at least two independent factors: (1) the inherent short-termvariability of sunlight due to cloud cover and other weather phenomena,and (2) the technological state of the art for a photovoltaic powerplant may be such that the instantaneous electricity output of the plantdirectly correlates to the amount of sunlight received at each moment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of a photovoltaic system with managedoutput, in accordance with an embodiment of the present invention.

FIG. 2 illustrates a flowchart representing operations in a method ofmanaging variability of output from a photovoltaic system, in accordancewith an embodiment of the present invention.

FIG. 3 illustrates a block diagram of an example of a computer systemconfigured for performing a method of managing variability of outputfrom a photovoltaic system, in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION

Photovoltaic systems with managed output and methods of managingvariability of output from photovoltaic systems are described herein. Inthe following description, numerous specific details are set forth, suchas specific approaches to reducing output, in order to provide athorough understanding of the present invention. It will be apparent toone skilled in the art that embodiments of the present invention may bepracticed without these specific details. In other instances, well-knowndata collection techniques, such as insolation data collection, are notdescribed in detail in order to not unnecessarily obscure embodiments ofthe present invention. Furthermore, it is to be understood that thevarious embodiments shown in the Figures are illustrativerepresentations and are not necessarily drawn to scale.

Disclosed herein are photovoltaic systems with managed output. In oneembodiment, a system includes a plurality of photovoltaic modulesconfigured to receive and convert solar energy. The system also includesa sensor configured to determine an orientation for each of theplurality of photovoltaic modules, the orientations based on a maximumoutput from the photovoltaic system. The system further includes anorientation system configured to alter the orientation of one or more ofthe plurality of photovoltaic modules to provide a reduced output fromthe photovoltaic system, the reduced output less than the maximumoutput.

Also disclosed herein are methods of managing variability of output fromphotovoltaic systems. In one embodiment, a method includes determiningan orientation for each of a plurality of photovoltaic modules, theorientations based on a maximum output from the photovoltaic system. Themethod also includes altering the orientation of one or more of theplurality of photovoltaic modules to provide a reduced output from thephotovoltaic system, the reduced output less than the maximum output. Inone embodiment, a method includes providing a plurality of photovoltaicmodules, each photovoltaic module having a solar energy collectioncapability. The method also includes reducing a solar energy collectioncapability of one or more of the plurality of photovoltaic modules toprovide a reduced output from the photovoltaic system, the reducedoutput less than a maximum output from the photovoltaic system.

In accordance with an embodiment of the present invention, intentionallyreducing the output of a photovoltaic system by purposefully tiltingaway from maximum collection orientation one or more solar modules froma plurality of solar modules in the system accommodates for a maximuminput capability at an associated power conditioner of a power plant.The maximum input capability at the power plant may be less than themaximum output of the associated photovoltaic system in some solarconditions. Other approaches may include de-tuning the power output ofthe photovoltaic system by manipulating an inverter between thephotovoltaic system and the power plant. Such de-tuning typicallyinvolves manipulating the real time system operating point along thecharacteristic I-V curve of the photovoltaic modules. However, inaccordance with at least some of the embodiments described herein,actually reducing the solar energy collection capability of thephotovoltaic system by redirecting or tilting away one or more of themodules may provide benefits versus detuning at the inverter level. Forexample, in an embodiment, such benefits may include, a slower responsetime to assuage blips in the system versus a very fast inverter changetime which may not be reducible, increased sensitivity to small changesin actual solar energy collection, more precise or granular control, orin cases when an inverter is actually offline. In an embodiment, suchbenefits may include eliminating or mitigating a compromise to inverterreliability.

Embodiments of the present invention may pertain to the functionalrequirements for tracker controller. For example, remote communicationand computational capabilities of a tracker controller may includeadvanced control features that may be implemented somewhat easily whencompared with other control approaches. Power plants that are associatedwith photovoltaic systems having tracker controllers are beingconstructed at an increasingly large scale and a central photovoltaicpower plant market is developing. As such, control challenges may becomeincreasingly important to resolve. In fact, it may be necessary toaddress this problem in order for a mature photovoltaic power plantmarket to grow to a significant scale. Embodiments of the presentinvention address this problem and are targeted for trackingphotovoltaic and concentrating photovoltaic power plants.

Throughout each day, a tracking photovoltaic power plant may adjust theorientation of its solar panels with respect to the sun so that thepanels receive the most direct sunlight possible, and thereby generatemore electricity than an otherwise identical non-tracking power plantwould. A concentrating photovoltaic power plant may use an opticalpackage to collect sunlight from a large area and focus this light ontoa smaller area of active solar cells (receiver). Throughout each day, aconcentrating photovoltaic power plant may be adjusted with respect tothe orientation of its collection optics pertaining to the position ofthe sun, such that the received sunlight is optimally focused onto thereceiver. In accordance with an embodiment of the present invention, aphotovoltaic system with managed output is applicable for both of thesetypes of power plants, although the details of implementation may varybetween flat plate photovoltaic and concentrating photovoltaicapplications.

Presently, tracking systems often orient their panels or optics in twobasic ways, neither of which are designed to provide the operator withcontrol of plant output. In a first approach, the tracking system willorient its panels or receivers into a series of positions that arepre-calculated based on the known position of the sun in the sky for theyearly cycle. In a second approach, the tracking position is constantlyadjusted based on feedback from optical sensors or the electrical outputfrom the photovoltaic array itself, and will thereby seek the brightestarea in the sky. In accordance with embodiments of the presentinvention, additional methods for controlling trackers that providecontrol of the power plant output are described. In one embodiment, theplant operator is enabled to control the electrical output of a trackingphotovoltaic or concentrating photovoltaic power plant to an extent thatmay not be possible with conventional approaches. In a specificembodiment, intelligent control of the tracking system is used todeliberately adjust plant output. In an embodiment, a photovoltaicsystem includes a sensor configured to determine an orientation for eachof the plurality of photovoltaic modules, the orientations based on amaximum output from the photovoltaic system. In one embodiment, theorientations are established for the purpose of collecting maximum solarenergy. In a specific embodiment, the maximum output is established at aparticular point in time, e.g., on a real-time basis.

Other methods for achieving this control functionality may includeemploying an energy storage system at the power plant, which can absorbenergy from an array or dispatch energy to the grid on command, andtherefore provide output control. However, at the present, no storagetechnology has yet been proven to be cost-effective for this specificapplication. By contrast, embodiments of the present invention may beimplemented at very low cost. Another approach includes using existingMaximum Power Point Tracking functionality contained in an inverter orin an array. This is a power electronics technology that can essentiallyde-tune the electrical performance of the system such that the outputfor the photovoltaic system is reduced. However, this approach may belimited in capability or reliability. On the other hand, embodiments ofthe present invention include additional control capability not possiblewith Maximum Power Point Tracking tuning or de-tuning alone.

In aspects of the present invention, three specific envisioned controlneeds include: (1) minimizing plant output variability from changingatmospheric conditions (for example, cloud cover), (2) generatingoutput-optimizing decisions, and (3) reduce cost by featheringphotovoltaic DC output during highest-performing conditions. Embodimentsof the present invention include one or more of the following features:(a) multiple solar tracking arrays, each containing tracking controllerscapable of responding to commands and adjusting the array trackingangles accordingly, (b) a weather monitoring or prediction center, (c) acommand center capable of making decisions either autonomously or withhuman operator input, with specialized software designed to perform theoperations and functions described herein, and (d) a communicationssystem which sends information and commands between the weathermonitoring or prediction center, command center, and the trackercontrollers.

With respect to specific envisioned control needs include (1), i.e.minimizing power plant output variability due to changing atmosphericconditions, the operation of embodiments of the present invention mayinclude one or more of the following features: (a) a weather monitoringor prediction center calculates the characteristics of futureatmospheric conditions over periodic intervals of time into the future,(b) a power plant system output is predicted over these periodicintervals of time into the future by the command center, based on thepredicted atmospheric conditions from (a), assuming that tracking iscarried out normally (e.g., based on an astronomical algorithm), (c) thecommand center evaluates the predicted power plant system output andmaximum acceptable ramp-rates (both up and down) set by the operator,and predicts future events in which the plant output ramp-rate willexceed the acceptable limits, (d) for future events predicted to exceedacceptable ramp-rate limits, the command center will calculate a uniquesolution, in which the tracking controllers adjust the tracking angle inanticipation of the changing atmospheric conditions, such that themaximum allowable ramp-rate is not exceeded, (e) an evaluation processtakes place to decide whether or not to implement each unique solution.In such an embodiment, solutions are evaluated automatically by thecommand center, and then possibly presented to the operator for decisionin some circumstances. Certain solutions may be pre-determined to be notpossible, possibly due to a limited amount of time that the system hasto respond, or limitations due to the maximum rate that tracking anglecan be changed. Such solutions may be disregarded by the command centerwithout operator input. Other solutions may meet certain objectivecriteria but not all, and therefore require operator decision andjudgment. Finally, some solutions may meet a full set of objectivecriteria and are decided upon by the command center. Additional featuresmay include: (f) implementing all solutions per the most recent solutiondefinition, (g) repeating the process outlined in (a)-(f) continuously.

With respect to specific envisioned control needs include (2), i.e.generating optimizing decisions, the operation of embodiments of thepresent invention may include one or more of the following features: (a)a weather monitoring or prediction center calculates the characteristicsof future atmospheric conditions over periodic intervals of time intothe future, (b) a power plant system output is predicted over theseperiodic intervals of time into the future by the command center, basedon the predicted atmospheric conditions from (a), assuming that trackingis carried out normally (e.g., based on astronomical algorithm), (c) acommand center models alternative tracking angles during future times inwhich the power plant output has fallen due to changing atmosphericconditions (e.g., during overcast conditions), and determines better orimproved tracking angles for increased power plant output during suchconditions (e.g., stowing the array), (d) optimized tracking events areimplemented, either autonomously or with operator input, (e) the processoutlined in (a)-(d) is repeated continuously.

With respect to specific envisioned control needs include (2), i.e.reducing cost by feathering photovoltaic DC output duringhighest-performing conditions, the operation of embodiments of thepresent invention may include one or more of the following features: (a)a weather monitoring or prediction center calculates the characteristicsof future atmospheric conditions over periodic intervals of time intothe future, (b) a power plant system output is predicted over theseperiodic intervals of time into the future by the command center, basedon the predicted atmospheric conditions from (a), assuming that trackingis carried out normally (e.g., based on astronomical algorithm), (c) thecommand center identifies predicted situations in which the plant outputwill exceed a set maximum design value. Such a design value may be usedto size many of the electrical components of the power plant, such asinverters and conductors, and could be exceeded very infrequently, suchas times of year that are very sunny, very cool and breezy. Additionalfeatures may include: (d) the command center calculates a trackingsolution in which the tracking arrays are de-tuned away from the sun,such that the maximum design output value is not exceeded, andimplements this solution either autonomously or with input fromoperator, (e) the process outlined in (a)-(d) is repeated continuously.

Embodiments of the present invention may be provided in the form ofsoftware which pre-calculates a variety of plant-output scenarios, andpresents the scenarios to a plant operator in a useful way for thepurpose of making decisions. In some embodiments, cost to be removedfrom the electrical design by ensuring that the highest possible outputof an associated photovoltaic system, which only happens veryinfrequently, is never provided to the power plant. In some embodiments,improved output on cloudy days may be achievable, without the need forguesswork by an operator.

In an aspect of the present invention, photovoltaic systems with managedoutput are described. FIG. 1 illustrates a block diagram of aphotovoltaic system with managed output, in accordance with anembodiment of the present invention.

Referring to FIG. 1, a photovoltaic system 100 has managed output.Photovoltaic system 100 includes a plurality of photovoltaic modules 102configured to receive and convert solar energy. Photovoltaic system 100also includes a sensor 104 configured to determine an orientation foreach of the plurality of photovoltaic modules 102, the orientationsbased on a maximum output from photovoltaic system 100. Also included isan orientation system (not shown) configured to alter the orientation ofone or more (e.g., sub-block 106) of the plurality of photovoltaicmodules 102 to provide a reduced output from photovoltaic system 100,the reduced output less than the maximum output. In an embodiment,photovoltaic system 100 further includes a power conditioning unit 108coupled with the plurality of photovoltaic modules 102, as depicted inFIG. 1.

In accordance with an embodiment of the present invention, theorientation system is configured to alter the orientation of the one ormore 106 of the plurality of photovoltaic modules 102 by tilting the oneor more 106 of the plurality of photovoltaic modules 106 away from adirect solar energy pathway. In one such embodiment, photovoltaic system100 further includes one or more solar tracker devices supporting theone or more 106 of the plurality of photovoltaic modules 102, andtilting the one or more 106 of the plurality of photovoltaic modules 102away from the direct solar energy pathway includes changing thepositioning of the one or more solar tracker devices. In anotherembodiment, the orientation system is configured to alter theorientation of the one or more 106 of the plurality of photovoltaicmodules 102 by tilting the one or more 106 of the plurality ofphotovoltaic modules 102 from a high intensity diffuse solar energypattern to a low intensity diffuse solar energy pattern. In one suchembodiment, photovoltaic system 100 further includes one or more solartracker devices supporting the one or more 106 of the plurality ofphotovoltaic modules 102, and tilting the one or more 106 of theplurality of photovoltaic modules 102 from the high intensity diffusesolar energy pattern to the low intensity diffuse solar energy patternincludes changing the positioning of the one or more solar trackerdevices. In a specific embodiment, the one or more solar tracker devicesincludes a device such as, but not limited to, single-axis trackers,e.g., a T10 or T20 Tracker available from SunPower Corp., of San Jose,Calif., U.S.A, or multi-axis trackers.

In accordance with an embodiment of the present invention, photovoltaicsystem 100 is coupled with a power plant. The maximum output fromphotovoltaic system 100 is greater than the capacity of the power plant,and the reduced output is less than or equal to the capacity of thepower plant.

In an embodiment, sensor 104 includes a pair of modules, each modulepositioned at a unique distance (e.g., L and L′) from the plurality ofphotovoltaic modules 102. In one embodiment, the pair of modules isconfigured to provide a delta in energy detected by the pair of modules.For example, the difference in detected solar radiation at one module issubtracted from the solar radiation detected at the second module andcorrelated with distance and bearing (e.g. L vs. L′). When a collectionevent is detected or anticipated, information gleaned from sensor 104may be used to determine how many modules to tilt away from maximumcollection positioning, and to what extent to the tilting should beperformed. Sensor 104 may further include or be associated withadditional sensing systems or data sources to better target real timechanges in energy input to the plurality of photovoltaic modules 102.For example, in an embodiment, sensor 104 further includes a network ofinsolation sensor modules arranged around the perimeter of, orinterspersed with, photovoltaic system 100. In another embodiment,sensor 104 further includes a network of still cameras or a combinationof still and video cameras. In an embodiment, photovoltaic system 100further includes a secondary sensor coupled with sensor 104, secondarysensor composed of a sensor such as, but not limited to, an anemometer,a wind vane, a satellite data source, or a temperature sensor. Inanother embodiment, photovoltaic system 100 further includes aneural-network configured to compute a value for the future change insolar energy detected by sensor 104.

In accordance with an embodiment of the present invention, powerconditioning unit 108 is configured to condition DC power from theplurality of photovoltaic modules 102. For example, in one embodiment,power conditioning unit 108 is an inverter, the inverter configured toinvert, to AC power, DC power from the plurality of photovoltaic modules102. In an alternative embodiment, power conditioning unit 108conditions DC power from the plurality of photovoltaic modules 102 andthen outputs the conditioned DC power.

In another aspect of the present invention, methods are provided formanaging variability of output from photovoltaic systems. FIG. 2illustrates a flowchart 200 representing operations in a method formanaging variability of output from a photovoltaic system, in accordancewith an embodiment of the present invention.

Referring to operation 202 of Flowchart 200, a method for managingvariability of output from a photovoltaic system includes determining anorientation for each of a plurality of photovoltaic modules, theorientations based on a maximum output from the photovoltaic system.

Referring to operation 204 of Flowchart 200, the method for managingvariability of output from a photovoltaic system further includesaltering the orientation of one or more of the plurality of photovoltaicmodules to provide a reduced output from the photovoltaic system, thereduced output less than the maximum output. In accordance with anembodiment of the present invention, altering the orientation of the oneor more of the plurality of photovoltaic modules comprises tilting theone or more of the plurality of photovoltaic modules away from a directsolar energy pathway. In one such embodiment, tilting the one or more ofthe plurality of photovoltaic modules away from the direct solar energypathway comprises changing the positioning of one or more solar trackerdevices supporting the one or more of the plurality of photovoltaicmodules. In accordance with another embodiment of the present invention,altering the orientation of the one or more of the plurality ofphotovoltaic modules comprises tilting the one or more of the pluralityof photovoltaic modules from a high intensity diffuse solar energypattern to a low intensity diffuse solar energy pattern. In one suchembodiment, tilting the one or more of the plurality of photovoltaicmodules from the high intensity diffuse solar energy pattern to the lowintensity diffuse solar energy pattern comprises changing thepositioning of one or more solar tracker devices supporting the one ormore of the plurality of photovoltaic modules. In an embodiment, when acollection event is detected or anticipated, information gleaned from asensor is used to determine how many modules to tilt away from maximumcollection positioning, and to what extent to the tilting should beperformed.

In accordance with another embodiment of the present invention, a methodfor managing variability of output from a photovoltaic system includesproviding a plurality of photovoltaic modules, each photovoltaic modulehaving a solar energy collection capability. The method also includesreducing a solar energy collection capability of one or more of theplurality of photovoltaic modules to provide a reduced output from thephotovoltaic system, the reduced output less than a maximum output fromthe photovoltaic system. In one embodiment, the maximum possible outputfrom the photovoltaic system is greater than the capacity of a powerplant coupled with the photovoltaic system, and wherein the reducedoutput is less than or equal to the capacity of the power plant.

In an aspect of the present invention, embodiments of the inventions areprovided as a computer program product, or software product, thatincludes a machine-readable medium having stored thereon instructions,which is used to program a computer system (or other electronic devices)to perform a process or method according to embodiments of the presentinvention. A machine-readable medium may include any mechanism forstoring or transmitting information in a form readable by a machine(e.g., a computer). For example, in an embodiment, a machine-readable(e.g., computer-readable) medium includes a machine (e.g., a computer)readable storage medium (e.g., read only memory (“ROM”), random accessmemory (“RAM”), magnetic disk storage media or optical storage media,flash memory devices, etc.).

FIG. 3 illustrates a diagrammatic representation of a machine in theform of a computer system 300 within which a set of instructions, forcausing the machine to perform any one or more of the methodologiesdiscussed herein, is executed. For example, in accordance with anembodiment of the present invention, FIG. 3 illustrates a block diagramof an example of a computer system configured for performing a method ofmanaging variability of output from a photovoltaic system. Inalternative embodiments, the machine is connected (e.g., networked) toother machines in a Local Area Network (LAN), an intranet, an extranet,or the Internet. In an embodiment, the machine operates in the capacityof a server or a client machine in a client-server network environment,or as a peer machine in a peer-to-peer (or distributed) networkenvironment. In an embodiment, the machine is a personal computer (PC),a tablet PC, a set-top box (STB), a Personal Digital Assistant (PDA), acellular telephone, a web appliance, a server, a network router, switchor bridge, or any machine capable of executing a set of instructions(sequential or otherwise) that specify actions to be taken by thatmachine. Further, while only a single machine is illustrated, the term“machine” shall also be taken to include any collection of machines(e.g., computers or processors) that individually or jointly execute aset (or multiple sets) of instructions to perform any one or more of themethodologies discussed herein.

The example of a computer system 300 includes a processor 302, a mainmemory 304 (e.g., read-only memory (ROM), flash memory, dynamic randomaccess memory (DRAM) such as synchronous DRAM (SDRAM), etc.), a staticmemory 306 (e.g., flash memory, static random access memory (SRAM),etc.), and a secondary memory 318 (e.g., a data storage device), whichcommunicate with each other via a bus 330. In an embodiment, a dataprocessing system is used.

Processor 302 represents one or more general-purpose processing devicessuch as a microprocessor, central processing unit, or the like. Moreparticularly, in an embodiment, the processor 302 is a complexinstruction set computing (CISC) microprocessor, reduced instruction setcomputing (RISC) microprocessor, very long instruction word (VLIW)microprocessor, processor implementing other instruction sets, orprocessors implementing a combination of instruction sets. In oneembodiment, processor 302 is one or more special-purpose processingdevices such as an application specific integrated circuit (ASIC), afield programmable gate array (FPGA), a digital signal processor (DSP),network processor, or the like. Processor 302 executes the processinglogic 326 for performing the operations discussed herein.

In an embodiment, the computer system 300 further includes a networkinterface device 308. In one embodiment, the computer system 300 alsoincludes a video display unit 310 (e.g., a liquid crystal display (LCD)or a cathode ray tube (CRT)), an alphanumeric input device 312 (e.g., akeyboard), a cursor control device 314 (e.g., a mouse), and a signalgeneration device 316 (e.g., a speaker).

In an embodiment, the secondary memory 318 includes a machine-accessiblestorage medium (or more specifically a computer-readable storage medium)331 on which is stored one or more sets of instructions (e.g., software322) embodying any one or more of the methodologies or functionsdescribed herein, such as a method for managing variability of outputfrom a photovoltaic system. In an embodiment, the software 322 resides,completely or at least partially, within the main memory 304 or withinthe processor 302 during execution thereof by the computer system 300,the main memory 304 and the processor 302 also constitutingmachine-readable storage media. In one embodiment, the software 322 isfurther transmitted or received over a network 320 via the networkinterface device 308.

While the machine-accessible storage medium 331 is shown in anembodiment to be a single medium, the term “machine-readable storagemedium” should be taken to include a single medium or multiple media(e.g., a centralized or distributed database, or associated caches andservers) that store the one or more sets of instructions. The term“machine-readable storage medium” shall also be taken to include anymedium that is capable of storing or encoding a set of instructions forexecution by the machine and that cause the machine to perform any oneor more of the methodologies of embodiments of the present invention.The term “machine-readable storage medium” shall accordingly be taken toinclude, but not be limited to, solid-state memories, and optical andmagnetic media.

It is to be understood that embodiments of the present invention may berelevant where the size of a photovoltaic system is such that it has amaterial impact on the operation or maintenance of a utility powersystem. In one embodiment, the material impact occurs at a level wherethe peak power of the photovoltaic system is significant relative to thepeak capacity of the portion of the grid the system that it is tiedinto. In a specific embodiment, the level is approximately above 10% ofa feeder, a substation, or a regulation service capacity. However, otherembodiments are not limited to such levels.

Thus, photovoltaic systems with managed output and methods of managingvariability of output from photovoltaic systems have been disclosed. Inaccordance with an embodiment of the present invention, a systemincludes a plurality of photovoltaic modules configured to receive andconvert solar energy. The system also includes a sensor configured todetermine an orientation for each of the plurality of photovoltaicmodules, the orientations based on a maximum output from thephotovoltaic system. The system also includes an orientation systemconfigured to alter the orientation of one or more of the plurality ofphotovoltaic modules to provide a reduced output from the photovoltaicsystem, the reduced output less than the maximum output. In oneembodiment, the orientation system is configured to alter theorientation of the one or more of the plurality of photovoltaic modulesby tilting the one or more of the plurality of photovoltaic modules awayfrom a direct solar energy pathway. In one embodiment, the orientationsystem is configured to alter the orientation of the one or more of theplurality of photovoltaic modules by tilting the one or more of theplurality of photovoltaic modules from a high intensity diffuse solarenergy pattern to a low intensity diffuse solar energy pattern.

What is claimed is:
 1. An apparatus comprising: a photovoltaic systemwith managed output, the system comprising: a plurality of photovoltaicmodules configured to receive and convert solar energy; a sensorconfigured to determine an orientation for each of the plurality ofphotovoltaic modules, the orientations based on a maximum output fromthe photovoltaic system; and an orientation system configured to alterthe orientation of one or more modules of the plurality of photovoltaicmodules to provide a reduced output from the photovoltaic system, thereduced output less than the maximum output, wherein the orientationsystem is configured to alter the orientation of the one or more modulesof the plurality of photovoltaic modules by tilting the one or moremodules of the plurality of photovoltaic modules away from a highintensity diffuse solar energy pattern to a low intensity diffuse solarenergy pattern, and wherein an output from the sensor is used todetermine how many modules to tilt away from maximum collectionpositioning, and to what extent to the tilting should be performed. 2.The photovoltaic system of claim 1, further comprising: one or moresolar tracker devices supporting the one or more modules of theplurality of photovoltaic modules, wherein tilting the one or moremodules of the plurality of photovoltaic modules away from the highintensity diffuse solar energy pattern to the low intensity diffusesolar energy pattern comprises changing the positioning of the one ormore solar tracker devices.
 3. The photovoltaic system of claim 1,further comprising: a power plant coupled with the photovoltaic system,wherein the maximum output from the photovoltaic system is greater thanthe capacity of the power plant, and wherein the reduced output is lessthan or equal to the capacity of the power plant.
 4. A methodcomprising: managing variability of output from a photovoltaic system,the managing comprising: determining an orientation for each of aplurality of photovoltaic modules, the orientations based on a maximumoutput from the photovoltaic system; and altering the orientation of oneor more modules of the plurality of photovoltaic modules to provide areduced output from the photovoltaic system, the reduced output lessthan the maximum output, wherein altering the orientation of the one ormore modules of the plurality of photovoltaic modules comprises tiltingthe one or more modules of the plurality of photovoltaic modules awayfrom a high intensity diffuse solar energy pattern to a low intensitydiffuse solar energy pattern, and wherein an output from the sensor isused to determine how many modules to tilt away from maximum collectionpositioning, and to what extent to the tilting should be performed. 5.The method of claim 4, wherein tilting the one or more modules of theplurality of photovoltaic modules away from the high intensity diffusesolar energy pattern to the low intensity diffuse solar energy patterncomprises changing the positioning of one or more solar tracker devicessupporting the one or more modules of the plurality of photovoltaicmodules.
 6. The method of claim 4, wherein the maximum output from thephotovoltaic system is greater than the capacity of a power plantcoupled with the photovoltaic system, and wherein the reduced output isless than or equal to the capacity of the power plant.
 7. Amachine-accessible non-transitory storage medium having instructionsstored thereon which cause a data processing system to perform a methodcomprising: managing variability of output from a photovoltaic system,the managing comprising: determining an orientation for each of aplurality of photovoltaic modules, the orientations based on a maximumoutput from the photovoltaic system; and altering the orientation of oneor more modules of the plurality of photovoltaic modules to provide areduced output from the photovoltaic system, the reduced output lessthan the maximum output, wherein altering the orientation of the one ormore modules of the plurality of photovoltaic modules comprises tiltingthe one or more modules of the plurality of photovoltaic modules awayfrom a high intensity diffuse solar energy pattern to a low intensitydiffuse solar energy pattern, and wherein an output from the sensor isused to determine how many modules to tilt away from maximum collectionpositioning, and to what extent to the tilting should be performed. 8.The machine-accessible non-transitory storage medium of claim 7, whereintilting the one or more modules of the plurality of photovoltaic modulesaway from the high intensity diffuse solar energy pattern to the lowintensity diffuse solar energy pattern comprises changing thepositioning of one or more solar tracker devices supporting the one ormore modules of the plurality of photovoltaic modules.
 9. Themachine-accessible non-transitory storage medium of claim 7, wherein themaximum output from the photovoltaic system is greater than the capacityof a power plant coupled with the photovoltaic system, and wherein thereduced output is less than or equal to the capacity of the power plant.